Assembling of hard disks essentially involves steps for fixing a magnetic head periphery with an adhesive. For example, such steps include fixing of piezoelectric elements, fixing of magnetic heads, and fixing of a magnetic head with a suspension (a head gimbal assembly (HGA)). The adhesives used in these steps require low-outgassing properties to prevent the occurrence of reading and writing errors ascribed to the outgas components being attached to the disk surface or the magnetic head. Such low-outgassing adhesives have been sought for. For example, Patent Literature 1 discloses an epoxy resin composition which contains an epoxy compound, a partially (meth)acrylated epoxy compound, a (meth)acrylic compound, an amine curing agent and a photoinitiator.